The clock may be ticking for your old air conditioner, especially if the unit is 10 years old or more. And with our weather heating up and the big summer heat on the horizon, you may be worried your unit’s time is up.

Well, now’s the perfect time to replace that old clunker-cooler. Soon it will be hot enough to wilt lettuce when you take it out of the refrigerator!

When considering AC contractors, you’ll want to use the same contractor guidelines we recommend when you hire any home improvement specialist.

Here are five key tips we pulled from our comprehensive AC consumer guide you’ll want to keep in mind:

1. Don’t do a half-baked job. You’ll want to consider the efficiency of the entire system, not just the AC unit. To avoid problems down the road, you may need to replace the furnace and air handler as well as the outside AC unit with its condenser and compressor so the entire system can run smoothly.

2. You can pump up the efficiency in your HVAC system. Repairing, resealing and reworking air ducts as part of the job can make a huge difference in your system’s efficiency. Before recommending a particular AC, the contractor should consider the duct efficiency, the size, shape and orientation of your home as well as the amount of insulation, windows, and number of people in the house.

3. Bigger is not always better. Recent improvements in air conditioning mean that you can buy fewer “tons” of cooling power for your house. A ton of refrigeration, by the way, is about equal to the cooling power of one ton of ice melting in 24 hours. Be wary of contractors who want to increase the tonnage of your new unit — and the price — because you have warm spots in your house. More tons will not solve the problem. You can generally drop about a half-ton in your new unit without even noticing it.

4. The lowest price is not always nice. Whether you get three bids or more, price is not your only criteria. That low bid might come from someone who hasn’t analyzed your ducts and who might not include a decent guarantee for parts and labor. A complete bid based on a complete analysis will be your best value.

5. Ask about the Energy Department’s SEER ratings. An Energy Star AC will have a Seasonal Energy Efficiency Ratio ranging from 13 to 21. This is something like miles per gallon with cars. The higher the SEER, the more efficient the air conditioner and the less costly to operate. Generally, an AC with a rating in the middle will probably work best and pay for itself more quickly in energy savings.

As always, you’ll want to make sure your contractor is experienced, well trained, registered with the state, and fully bonded and insured. Of course all of our Rosie Air Conditioning contractors meet these criteria and have made it through our strict Rosie-Certified Partner Qualification process.

You can find more advice and do-it-yourself tips, for your house, home, castle or cabin, at every Arizona homeowner’s best friend: Rosie on the House. And, if you’re looking for the very best contractor or service provider for your home improvement projects, always trust a Rosie-Certified Partner — Arizona’s most trusted Referral Network.

Be sure to tune in to KTAR every Saturday morning from 7-11 a.m. for the Rosie on the House broadcast!